Examples of known molding systems are (amongst others): (i) the HyPET™ Molding System, (ii) the Quadloc™ Molding System, (iii) the Hylectric™ Molding System, and (iv) the HyMet™ Molding System, all manufactured by Husky Injection Molding Systems Limited (Location: Bolton, Ontario, Canada; www.husky.ca).
Metal injection molding (MIM) is a manufacturing process which combines the versatility of plastic injection molding with the strength and integrity of machined, pressed or otherwise manufactured small, complex, metal parts. The window of economic advantage in metal injection molded parts is such that the complexity and small size of the part or perhaps difficulty of fabrication through other means make it cost inefficient or impossible to manufacture otherwise. Increasing complexity for traditional manufacturing methods typically does not increase cost in a metal injection molding operation due to the wide range of features possible through injection molding (features such as: undercuts, thread both internal and external, miniaturization, etc.).
U.S. Pat. No. 4,694,881 (Inventor: Busk; Published: Sep. 22, 1987) discloses thixotropic alloy production by heating alloy above its liquids, cooling to between solidus and liquidus, and shearing in an extruder. More specifically, this patent appears to disclose a process for forming a liquid-solid composition from a material which, when frozen from its liquid state without agitation, forms a dendritic structure. A material having a non-thixotropic-type structure, in a solid form, is fed into an extruder. The material is heated to a temperature above its liquidus temperature. It is then cooled to a temperature less than its liquidus temperature and greater than its solidus temperature, while being subjected to sufficient shearing action to break at least a portion of the dendritic structures as they form. Thereafter, the material is fed out of the extruder.
U.S. Pat. No. 5,685,357 (Inventor: Kato et al; Published: Nov. 11, 1997) discloses metal molding manufacturing with good mechanical strength, the process includes melting solid metal in cylinder barrel of an injection molding machine. More specifically, this patent appears to disclose a metallic feed initially in a solid state that is fed into a cylinder barrel of an injection molding machine. The metallic feed is melted by applying heat to the metallic feed from outside the cylinder barrel and by heat produced from frictional and shearing forces generated by rotation of a screw housed within the cylinder barrel. The cylinder barrel and screw define at least a feed zone, a compression zone and an accumulating zone. After melting and passing through each of the three zones, the metallic feed is injected into a die, to thereby form a shaped part. The temperature of the metallic feed is controlled to be above the liquidus of the metallic feed during the injecting process.
U.S. Pat. No. 5,983,976 (Inventor: Kono; Published: Nov. 16, 1999) discloses injecting a molten material into a die-casting mold. More specifically, this patent appears to disclose an injection molding system that includes a feeder in which a metal is melted, and a first chamber into which a desired amount of melted metal is introduced. A piston in a second chamber first retracts to create suction, assisting in drawing in the melted metal into the second chamber from the first chamber and evacuating gas. A ram then pushes some melted metal remaining in the first chamber into the second chamber, forcing out gas present in the second chamber. The piston then injects the melted metal out of the second chamber into a mold. The melted metal is preferably maintained in a liquid state throughout the system.
U.S. Pat. No. 6,241,001 (Inventor: Kono; Published: Jun. 5, 2001) discloses manufacturing a light metal alloy for injection molding with desired characteristics of density in a consistent manner. More specifically, this patent appears to disclose an injection molding system for a metal alloy. The injection molding system includes a feeder in which the metal alloy is melted and a barrel in which the liquid metal alloy is converted into a thixotropic state. An accumulation chamber draws in the metal alloy in the thixotropic state through a valve disposed in an opening between the barrel and the accumulation chamber. The valve selectively opens and closes the opening in response to a pressure differential between the accumulation chamber and the barrel. After the metal alloy in the thixotropic state is drawn in, it is injected through an exit port provided on the accumulation chamber. The exit port has a variable heating device disposed around it. This heating device cycles the temperature near the exit port between an upper limit and a lower limit. The temperature is cycled to an upper limit when the metal alloy in the thixotropic state is injected and to a lower limit when the metal alloy in the thixotropic state is drawn into the accumulation chamber from the barrel.
U.S. Pat. No. 6,789,603 (Inventor: Kono; Published: Sep. 14, 2004) discloses injection molding of metal (such as magnesium alloy) that includes the following steps: (i) providing a solid metal into melt feeder, (ii) melting the solid metal into a liquid state, (iii) providing the liquid metal into an inclined metering chamber, (iv) metering metal, and (v) injecting the metal into a mold. More specifically, this patent appears to disclose metal injection molding method, that includes the following steps: (i) providing solid metal into a melt feeder, (ii) melting the solid metal into a liquid state, such that a fill line of the liquid metal is below a first opening between an inclined metering chamber and a first driving mechanism, (iii) providing the liquid metal into the inclined metering chamber containing the first driving mechanism attached to an upper portion of the metering chamber, (iv) metering the metal from the metering chamber into an injection chamber located below a lower portion of the metering chamber, and (v) injecting the metal from the injection chamber into a mold.
U.S. Pat. No. 7,066,236 (Inventor: Fujikawa; Published: Jun. 27, 2006) discloses an injection device for a light metal injection molding machine, which extrudes molten metal formed by fusing a cylinder from inserted billets, and injects molten metal when billets are passed through connection element. More specifically, this patent appears to disclose an injection device for a light metal injection molding machine that includes: (i) a melting device for melting light metal material into molten metal, (ii) a plunger injection device for carrying out injection of molten metal using a plunger after the molten metal is metered into an injection cylinder from the melting device, (iii) a connecting member including a connecting passage for connecting the melting device and the plunger injection device, and (iv) a backflow prevention device for preventing backflow of molten metal by opening and closing the connecting passage.
A technical article (published in 2004 by Elsevier B. V.; titled “The generation of Mg—Al—Zn alloys by semisolid state mixing of particulate precursors”; authored by Frank Czerwinski; published in a technical journal called Acta Materialia 52 (2004) 5057-5069) discloses a number of Mg—Al—Zn alloys with thixotropic microstructures that were created by the semisolid mixing of AZ91D and AM60B mechanically comminuted precursors in a thixomolding system. The microstructure formation was analyzed along with the role of structural constituents in controlling strength, ductility and the fracture behavior of the created alloy. It was found that the inhomogeneity in the partition of alloying elements intensified with a reduction in the processing temperature and the liquid fraction was highly influenced by the alloy with the lower melting range. Tensile strength showed a strong correlation with corresponding elongations and was predominantly controlled by the solid particles' content in the microstructure, with negligible influence derived from changes in the alloy's chemistry. Although elongation was affected by both the solid content and the alloy's chemical composition, a larger role was still exerted by the former. The contribution of individual precursors to the tensile properties of the created alloy depended on the processing temperature. While near to complete melting, both of them contributed almost equally; with a temperature reduction, the deviation from the rule of mixtures enlarged, and properties were increasingly influenced by the precursor with the lower melting range.
A technical article (published in 2005 by Elsevier B. V.; titled “A novel method of alloy creation by mixing thixotropic slurries”; authored by Frank Czerwinski; published in a technical journal called Materials Science and Engineering A 404 (2005) 19-25) discloses the concept of semisolid processing to generate alloys by mixing coarse particulate precursors with different chemistries. Experiments with several magnesium alloys revealed that the control of chemistry and the proportion of precursors, as well as the solid to liquid ratio during their partial melting, allowed the selective partition of alloying elements between the solid and liquid phases, thus designing unique solidification microstructures.
A technical article (published in 2005 by SAE International; titled “The Concept and Technology of Alloy Formation During Semisolid Injection Molding”; authored by Frank Czerwinski; published in a technical journal called SAE Technical Paper Series) discloses the application of semisolid technologies for processing magnesium alloys. The benefits of using the semisolid state and processing capabilities of Husky's thixosystem are introduced. The main attention is focused on exploring Thixomolding® for the generation of alloys by the mixing and partial melting of particulate precursors with different chemistries. Experiments with magnesium-based precursors revealed that the partition of alloying elements between the liquid matrix and remaining primary solid as well as the microstructure of created alloys were controlled by the processing temperature.